In support of our hypothesis that ATP depletion underlies liver injury in patients with NAFLD, our group has demonstrated that patients with biopsy-proven NAFLD have increased hepatic mRNA expression of KHK compared to matched controls. Indeed, in human pilot studies, intravenous (IV) fructose administration is associated with hepatic ATP depletion which can be assessed by 31P magnetic resonance spectroscopy (MRS). Reduced hepatic ATP stores are more prevalent in overweight and obese subjects than in lean subjects. Furthermore, recovery from fructose-induced ATP depletion was found to be delayed in patients with NAFLD (n=8). However, a limitation to this existing work is the small sample size and the inability to assess a cause-effect relationship(s) between BMI, NAFLD, energy homeostasis, and histologic features of liver injury. In liver cells, ATP depletion could perpetuate chronic liver injury by making fatty hepatocytes less proliferative. Hepatic ATP depletion also encourages the expansion of liver progenitor populations, causes arrest in protein synthesis, induces inflammatory and prooxidative changes, increases endoplasmic reticulum stress, promotes activation of stress-related kinases, induces mitochondrial dysfunction, and increases apoptotic activity. This supporting data suggests that fructose may be associated with NAFLD, NASH, and progressive fibrosis. Further, a study by Loguercio et al. demonstrated that increased uric acid levels above the basal level after IV fructose infusion was significantly higher (p < 0.01) in patients with cirrhosis (3 mg/dl) and NASH (1.9 mg/dl) than in healthy controls (1.2 mg/dl). This effect was completely reversed by fructose 1,6-diphosphate which could replenish the ability to resynthesize ATP from ADP. Therefore, an IV fructose challenge could effectively differentiate healthy subjects, from chronic hepatitis, from cirrhosis.